Tubular structural unit and method of making the same



Jan. 28, 1936. H. N. ATwooD 2,029,048

TUBULAR STRUCTURAL UNIT AND METHOD OF MAKING THE SAME Filed July 3 1, 1934 Hqzvyjwoodl Patented Jan. 28, 1936 UNITED STATES PATENTV FFICE TUBULAB STRUCTURAL UNIT AND METHOD F MAKING THE 9 Claims.

This invention relates to a tubular structural unit and method of making the same.

The object of the invention is to provide a laminated structural unit which is light in weight and strong and durable in construction, thereby rendering it particularly adapted for use in the construction ci all kinds of air and marine craft and for various other purposes.

A further object of the invention is to provide a structural unit formed of laminated tubes preferably impregnated with rubber and united one to the-other in substantially at formation to form a cellular structure, the exterior of which is coated with cellulosic plastic material to impart a case-hardened finish thereto.

A further object of the invention is to so construct, assemble and unite thelaminated tubes as to permit exng or bending of the assembled structure to conform to any desired shape so that when the cellulosic material is applied and the structure subjected to heat and pressure, it will take a xed or permanent form.

' The invention consists in Winding, preferably rubber impregnated strips of wood veneer or other fibrous material, around suitable shaping mandrels in superposed layers to form independent laminated tubes, pressing the tubes together in at formation to cause the adjacent adhesive surfaces to unite and permit flexing or shaping of the assembled structure; immersing the assembled structure in an acetone solution containing ak small percentage of cellulosic plastic material and subsequently inserting finishing mandrels within the tubes and subjecting the structure to heat and pressure to vulcanize the parts and cause them to retain a fixed denite shape.

In the accompanying drawing forming a part of this specication and in which similar numerals of reference indicate corresponding parts in all the views of the drawing:

Figure 1 is a perspective view of a strip of natural wood veneer prior to impregnatlng the same with rubber.

Figure 2 is a vertical sectional view showing the veneer strip immersed in a rubber or latex solution.

Figure 3 is a side elevation showing the manner of ceiling or wrapping the rubberized veneer on a shaping mandrel.

Figure 4 is a perspective View, partly broken away showing several of the tubes assembled side by side and bonded together, the flexing of the tubes being indicated by dot and dash lines.

Figure 5 is a vertical sectional view showing the assembled tubes immersed in an acetone solution containing cellulosic plastic material.

Figure 6 is a vertical sectional view, partly in section, showing the assembled tubes supported on mandrels between pressing and heating ele- 5 ments to effect vulcanization.

Figure 7 is a sectional perspective view of a portion of the completed structural unit.

Figure 8 is a detail sectional view taken on the line 8-8 of Figure '7 showing how the rubber and 10 cellulosic plastic material is bonded to the wood.

Figure 9 is an end elevation illustrating a modifled form of the invention.

Figure 10 is a detail perspective showing the tubes assembled in a different manner.

According to the present invention, I take thin strips 6 of fibrous material, preferably natural wood veneer, and these strips may be, of any desired length, width and thickness, although it is preferred that the thickness of the strips be approximately one-forty-eighth of an inch. The strip or strips 6 are then preferably placed in a tank 'l containing a rubber or latex solution 8 and allowed to remain therein until the wood is impregnated or partially impregnated with the rubber', at which time the strips will present a sticky adhesive surface, indicated at 9. The rubberized strips are then wound or coiled around a cylindrical mandrel I0, although a mandrel of any other desired cross sectional shape may be employed. The wood veneer strips are preferably wound in spiral superposed layers Il with the adjacent edges of the veneer strips of the foundation layer abutting and with the next succeeding layer overlapping the foundation layer and in intimate contact therewith so as to form a tubular member l2. Any number of layers of veneer may be employed according to the strength and stability desired. Inasmuch as the veneer strips are surfaced with the rubber when the strips are coiled around the mandrel, a close adhesion between the strips will result and the body of the tube will be formed; in eifect, of alternate layers of wood and rubber securely bonded together.

After having formed the tubes in this man- -ner, said tubes are assembled side by side with their adhesive surfaces in intimate contact with each other, as best shown in Figure 4 of the drawing, and, if desired, while the tubes are thus assembled the contacting surfaces may be vulcanized so that a exible structure is produced which may be bent in any direction, as indicated by the dot and dash lines in Figure 4 of the drawing, and thus permit the assembled tubes to assume any desired shape. If the structural furthergmodication in which the tubes 23 are unit is to be at, the tubes are assembled in horiassembled in angular formation, this construczontal alinement lyith each other and then imtion being particularly adapted for use in the mersed iii a tank 33 of acetone solution I4 confabrication of sound-proof cabinets and similar taining approximately ve percent, by weight, of estructuras.

solid celll'ilosic plastic material such as cellulose While a product constructed in accordance acetate, cellulose nitrate or cellulose ester and with the present invention is especially adapted allowed tei remain therein until the cellulose ma- Qfor use in the fabrication of aeroplane and other terial entirely covers the inner and outer surfaces air and ,water craft, it will, of course, be under- V of the tubes so as to form a hard protective stood that said product may be :used in the concjeating or jacket therefor. The assembled tubes i struction of buildings or wherever a structural tiius treated aremthen placed on auxiliary 0r unit of this character is foundjlecessary or delnishing mandrels I5 andn said assembled tubes "sirable, It will also be understoed that the strucinserted between coacting pressing elements or tural units may be made in di'iferent sizes and rsolds iiheated te the desired temperature and shapes' withoutdeparting frorn'the spirit or tbe the tubes subjected to heat and pressure to vulinvention. canize the parts and retain the assembled tubes Having thus described the invention, I claim: in permanent form. i; l. A structural unit 'fromprising tubular mem- If a curved unit is desired, the assembled tubes "bers bonded together side by side to form e, Sub- 2o may be eXed t0 the desired euriature er shape stantiaily flat built up structure, and a coating before immersion in the acetone solution and consisting of an acetone solution containing ce1- subsequently dipped in said SOlutiOu and sublulosic plastic fmaterial covering said built up jected to'heat and pressure whereby the hard structure, j i protective jacket or coating of cellulosic mate- 2. A structural unit comprising tubular memrial will retain the assembled tubes permauentbers assembledf side by side with their adjacent 1y in the desiredshape VThe application 0f heat surfaces in intimate contact and bonded togethand pressure t0 elle tubes not Gull? serves t0 vuler, and a coating of cellulosic plastic material eanize the rubber and Cause it te penetrate the covering the assembled tubes and bonded thereto. fibers of the wood but also causes the plastic ma- 3l Agr structural unit comprising a plurality of terial to ow uniformly over the exterior theretubuleg members formed of rubber impregnated of and enter and cover any cracks or interstices i wood ueneer 1emibati0ne, Seid membersbeng es, which may nOt leave been lled With the YubbelfY sembl-d side by side and bonded together by the The plastic material alsowlls the Spaces betWeell'; rubber with which the laminations are impregthe tubes, aS indicated at Il, and Provides 2f nated,Y and cellulosic plastic material orming a .35 smooth hard Water-pr00f DiSh t0 the strueturef hard smooth protective jacket for the assembled Ythereby Yenabling'it to withstand the deleterious;V tubes and ailing tbe spaces between Ythe tubes iaction of the elements for an indefinite period. j and bonded theretm BY reference .t0 Figure '7 0f the drawing, itii 4. A'structural unit comprising a pljilrality of .Will be noted that each 0f the assembled tubes tubular members assembled lside by side and 4o iles an vinner coating I8 of ceuulosic plastic ma-Y unitedby a flexible bonding agent to allow exing YYserial. and an outer coating I9 of the same maof the essembed tubes and permit them to as.. erdl aud between Which are utelpsei Spiralsure a desired shape, Yand a coating of'cellulosic arranged rubber impregnated wood veneer plastic material covering the assembled tubes strips thereby giving the produet the necessary for holding said tubes'in nxedpositioneand protoughness and Strength t0 resisttensile end tOividing a hard exterioliprotective jacket therefor.

sional strains when in use- 5. A structural unitel comprising a plurality of A structural unit Constructed in acuerde-nce independent tubular members formed of rubber With the present inventif-)u is light in Weight end impregnated wood veneer strips, said tubes being tough in texture s0 thatiit is particularly sdaptassembled side by side with their adjacent faces to Yed for use in the fabrication 0f the fuselage and in contact and bonded together Yby the rubber with Other Darts 0f au' und Wetel' Oraft- Furthermore. which the strips are impregnated, and cellulosic as the structural unit iieellularein fermtieu, it plastic material forming a coating for the inner is extremely buyant and will prevent Wsinking walls of the tubular members and the outer walls of air craft in ease of disaster when flying Over thereof, said eellulosic material tllling the spaces a body of water. between the tubes -and forming a hard exterior While it is preferred te impreenate the wood surfaee entirely surroundlngand covering tno n veneer strips with rubber prior to the application tubes;

0f the CellulOsle Dlastlefmeterlal thereto, if de- 6. structural unit comprising a plurality of sli'eil, in Certe-12 Cases aud uudefl Certain COIld'f' tubular members impregnated with rubber and so' tions, tbe rubber may be omitted and the aeef; assembled side by side" with their adjacent adrie- Ytone.SOutlOIl auplled directly t0 the WOOd veueeif sive surfaces in intimate contact and Ybonded tostrips prior to coiling the same in tube form andV gether, rubberized wood veneer reinforcing memduring aud aft-er said ceiling Operation and bers Ydisposed on opposite sides of tile tubular thel'efQe d0 Het desire t0 limit the invention in members, and a. protective Yjacket o cellulosic o5 this respect. plastic material surrounding the tubes and rein- InvFigure 9 of the drawing, there is illustrated a forcing members and intimately connected with modified form of the invention in which the tubuand bonded thereto. lar members 2e are preferably restarsolar in 7. The method of making a tubular structural cross section. in this form of the device, the unit which consists in winding strips cf wood 70 structure is preferably reinforced and strengthveneer on a shaping mandrel superposed spiral ened by the provision of upper .and lower strips layers to form a tubular member, assembling sev- 2| of wood veneer impregnated with rubber and eral of said tubular members side by side with coated with a cellulosic plastic material 22 in the their adjacent surfaces in bonding contact, apmanner previously stated. plying an acetone solution containing cellulosic 7s In Figure 10 of the drawing, there is shown a plastic. material to the outer surfac of the as- 75 l sembled tubes, and subsequently subjecting the assembled tubes to heat and pressure. 8. The method of making a. tubular structural unit which consists in covering a strip of wood veneer with a rubber solution to impregnate the wood with rubber and impart thereto a surface adhesion, winding the veneer strip on a shaping mandrel to form a tubular member. assembling several of said tubular members with their adhesive surfaces in contact, immersing the assembled tubular members in an acetone solution containing cellulosic plastic material to entireIy cover the inner and outer surfaces of the assembled tubes, and subsequently subjecting the assembled tubes thus treated to heat and pressure. 9. The method of making a tubular structural unit which consists in impregnating a strip oi I wood veneer with a. rubber solution, winding the veneer strip on a shaping mandrel to form a. tubular member, assembling several of said tubular members side by side with the adjacent contacting faces of the members bonded together, immersing the assembled tubular members in an acetone solution containing a small percentage of cellulosic plastic material to cause'the cellulosic plastic material to cover the interior and exterior of the tubular members and fill the spaces between said members, inserting auxiliary mandrels within the tubular members, and placing the assembled tubular members While on the auxiliary mandrels between suitable pressing members and subjecting the same to heat and pressure thereby to cause the cellulosic material to entirely cover the tubular members and present a hard smooth finish.

HARRY N. ATWOOD. [L.S.] 

